In general, a microelectronic device, e.g. a semiconductor device, may be processed in microfabrication technology, e.g. in semiconductor technology, on and/or in a substrate (also referred to as a wafer or a carrier). The substrate may include a plurality of microelectronic devices, e.g. chips, which are processed or mounted in corresponding regions of the substrate. For fabricating such semiconductor devices, certain electrical contact structures are provided by forming layers and layer stacks, e.g. for electrical interconnections between at least two microelectronic devices or between at least one microelectronic devices and the substrate (e.g. a printed circuit board).
Conventionally, for forming layers and layer stacks a broad variety of materials is processed, e.g. structured, e.g. by etching. However, materials which are processable by etching are also vulnerable regarding environmental influences, e.g. during further process steps, and tend to deteriorate, e.g. by oxidation. The deterioration may impair the functionality of the layers, e.g. their capability for providing electrical connections. Therefore, environmental resistant protection layers may be used for protecting the vulnerable layers against environmental influences. However, materials which provide a high environmental resistance are hard to process by etching due to their high resistance and protection qualities. This complicates the fabrication processes and increases the number of process steps necessary to form the respective layer stacks. Illustratively, the materials usable for protection are also resistant against a wide range of processing technologies.
On order to avoid etching, a layer is deposited on a structured mask which is used as sacrificial layer and removed together with the unwanted parts of the layer (also referred to as lift-off process). However, the lift-off process limits the thickness of the layer due to the limited mask thickness. The limited thickness of the layer impairs its capability to provide a stable electrical contact, e.g. using soldering. Illustratively, the lift-off processed layer is too thin to provide a stable electrical contact. Therefore this technique is limited in providing suitable protection layers for electrical contacts.